In this work we report on a study of the morphological changes of LDL induced in vitro by metallic ions (Cu(2+) and Fe(3+)). These modifications were characterized by transmission electron microscopy, nuclear magnetic resonance and the Z-scan technique. The degree of oxidative modification of LDL was determined by the TBARS and lipid hydroperoxides assays. It is shown that distinct pathways for modifying lipoproteins lead to different morphological transformations of the particles characterized by changes in size and/or shape of the resulting particles, and by the tendency to induce aggregation of the particles. There were no evidence of melting of particles promoted by oxidative processes with Cu and Fe. (C) 2010 Elsevier Ireland Ltd. All rights reserved.; State of Sao Paulo Research Foundation (FAPESP); National Institute of Science and Technology of Complex Fluids (INCT-FCx); National Counsel of Technological and Scientific Development (CNPq)

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP); Processo FAPESP: 06/02121-6; Processo FAPESP: 11/01937-0; NC2 (R) tricot stitched carbon preform has been tested to evaluate its potential application in aircraft structures. It is one in a range of stitched fabric group, specially developed by Hexcel Composites, designed to be processed with a RTM6 monocomponent resin. This article aims to evaluate the tricot stitched fabric behavior towards resin flow front in resin transfer molding process, its mechanical performance in bending test, and its structure during C-scan non-destructive inspection. Flexural performance of the laminates and the scatter of the results corresponded well with C-scan ultrasonic maps, where resin pockets near the stitches were distinguished. The fracture area visualization, via photography and scanning electron microscopy techniques, aided to find a few flaws between the stitch yarns, which conducted to a larger scatter of the flexural rupture strength results.

The morphology and the existence of a growth cycle of Mycoplasma pneumoniae have not been clearly established. There is disagreement as to whether this organism exists as a spherical or filamentous form, and whether it progresses from filamentous to spherical forms as the organism ages. A scanning-beam electron microscope (SEM) was utilized to provide detailed observations of the cycle of morphological changes during growth phases of M. pneumoniae. Cultures of cells grown and fixed in liquid suspension displayed morphological changes from spherical to filamentous and then to larger round forms. After 8 hr to 2 days of growth (phase I), spherical forms and aggregates were revealed. Two- to 6-day-old growth (phase II) was composed of both straight and branching filaments with bulbous elements situated at intervals along their lengths, and microcolonies composed predominantly of intertwined filaments. Six- to 10-day-old growth (phase III) was characterized by flattened, spherical organisms larger than those observed in phase I, occasional membranes or ghosts, and a paucity of aggregates or microcolonies. Thus, stereo-scan electron microscopic studies suggest that M. pneumoniae undergoes an orderly and sequential metamorphosis during its life cycle.

High-resolution images of orthorhombic purple membrane have been obtained by electron cryomicroscopy with spot-scan illumination, and the projection structure at 3.9 Å resolution calculated after image processing and averaging of the data. Since the phases of the structure factors in the projection down the orthorhombic twofold axis should be either 0 or 180°, this offers the first opportunity to make an independent test of the estimated accuracy of high-resolution phases obtained by electron microscopy. The results show the final phases are less accurate than previously estimated by a small factor (1.3). Careful comparison of the new orthorhombic structure to the known trigonal structure shows only small differences after account is taken of a slight difference in the tilt angle of the molecules in the two crystals. This is consistent with the available kinetic and spectroscopic data which show very small differences in behavior.

Electron microscopists are increasingly turning to intermediate voltage electron microscopes (IVEMs) operating at 300–400 kV for a wide range of studies. They are also increasingly taking advantage of slow-scan charge coupled device (CCD) cameras, which have become widely used on electron microscopes. Under some conditions, CCDs provide an improvement in data quality over photographic film, as well as the many advantages of direct digital readout. However, CCD performance is seriously degraded on IVEMs compared to the more conventional 100 kV microscopes. In order to increase the efficiency and quality of data recording on IVEMs, we have developed a CCD camera system in which the electrons are decelerated to below 100 kV before impacting the camera, resulting in greatly improved performance in both signal quality and resolution compared to other CCDs used in electron microscopy. These improvements will allow high-quality image and diffraction data to be collected directly with the CCD, enabling improvements in data collection for applications including high-resolution electron crystallography, single particle reconstruction of protein structures, tomographic studies of cell ultrastructure, and remote microscope operation. This approach will enable us to use even larger format CCD chips that are being developed with smaller pixels.

Fast-scan cyclic voltammetry with carbon-fiber microelectrodes has been successfully used to detect catecholamine release in vivo. Generally, waveforms with anodic voltage limits of 1.0 V or 1.3 V (vs. Ag/AgCl) are used for detection. The 1.0 V excursion provides good temporal resolution, but suffers from a lack of sensitivity. The 1.3 V excursion increases sensitivity, but also increases response time which can blur the detection of neurochemical events. Here, the scan rate was increased to improve the sensitivity of the 1.0 V excursion while maintaining the rapid temporal response. However, increasing scan rate increases both the desired faradaic current response and the already large charging current associated with the voltage sweep. Analog background subtraction was used to prevent the analog-to-digital converter from saturating from the high currents generated with increasing scan rate by neutralizing some of the charging current. In vitro results with the 1.0 V waveform showed approximately a four-fold increase in signal to noise ratio with maintenance of the desired faster response time by increasing scan rate up to 2400 V/s. In vivo, stable stimulated release was detected with an approximate four-fold increase in peak current. The scan rate of the 1.3 V waveform was also increased...

Monte Carlo softwares are widely used to understand the capabilities of electron microscopes. To study more realistic applications with complex samples, 3D Monte Carlo softwares are needed. In this paper, the development of the 3D version of CASINO is presented. The software feature a graphical user interface, an efficient (in relation to simulation time and memory use) 3D simulation model, accurate physic models for electron microscopy applications, and it is available freely to the scientific community at this website: www.gel.usherbrooke.ca/casino/index.html. It can be used to model backscattered, secondary, and transmitted electron signals as well as absorbed energy. The software features like scan points and shot noise allow the simulation and study of realistic experimental conditions. This software has an improved energy range for scanning electron microscopy and scanning transmission electron microscopy applications.

Transmission-mode scanning electron microscopy (tSEM) on a field emission SEM platform was developed for efficient and cost-effective imaging of circuit-scale volumes from brain at nanoscale resolution. Image area was maximized while optimizing the resolution and dynamic range necessary for discriminating key subcellular structures, such as small axonal, dendritic and glial processes, synapses, smooth endoplasmic reticulum, vesicles, microtubules, polyribosomes, and endosomes which are critical for neuronal function. Individual image fields from the tSEM system were up to 4,295 µm2 (65.54 µm per side) at 2 nm pixel size, contrasting with image fields from a modern transmission electron microscope (TEM) system, which were only 66.59 µm2 (8.160 µm per side) at the same pixel size. The tSEM produced outstanding images and had reduced distortion and drift relative to TEM. Automated stage and scan control in tSEM easily provided unattended serial section imaging and montaging. Lens and scan properties on both TEM and SEM platforms revealed no significant nonlinear distortions within a central field of ∼100 µm2 and produced near-perfect image registration across serial sections using the computational elastic alignment tool in Fiji/TrakEM2 software...

In this study, we present the scanning force and electron microscopic visualization of single molecules of fibronectin either frozen hydrated or adsorbed onto metallic and polymeric surfaces with different solid surface tensions. The surfaces were characterized by dynamic contact angle measurements, X-ray photo emission spectroscopy (XPS or ESCA) and scanning force microscopy. The proteins were prepared by fast protein liquid chromatography (FPLC) and characterized by gel electrophoresis. Protein films on surfaces were investigated by surface plasmon resonance spectroscopy and directly imaged by scanning force microscopy. The spreading of the adsorbed fibronectin revealed dependence on the chemical composition and the solid surface tension. Structure of fibronectin in solution as well as on solid interface appeared as an extended straight strand as obtained by imaging with electron and scanning probe microscopies. Imaging of DNA was performed by scanning force microscopy to test the accuracy and reproducibility of our measurements. The measured contour lengths were accurate and the larger widths were caused by convolution of the tip shape and sample. Frictional forces during the scan have been of significant contribution in the imaging mechanism. Moreover...

AIM: To measure the fracture resistance of over-flared roots filled with a variety of materials (gutta-percha-nano HA, resilon-epiphany, composite and mineral trioxide aggregate - MTA) using the Instron machine test and micro-computed tomography (Micro CT) Scan. In addition, scanning electron microscopy (SEM) images were used to illustrate the type of fracture patterns of the specimens. METHODS: One hundred and twenty extracted human mandibular single-rooted premolars were selected. A total of 105 out of the selected teeth were prepared to the working length and over-flared, leaving the apical 5 mm undisturbed. Fifteen samples had no treatment and were used as a positive control group (Group +ve). The 105 test teeth were further divided into 7 groups of 15 samples each. One of the 7 groups was designated as negative control (Group -ve) where teeth were over prepared and left without obturation. Remaining groups were filled with gutta-percha-nanoHA (Group1), gutta-percha-nano HA+composite (Group 2), gutta-percha-nano HA+MTA (Group 3), resilon-epiphany (Group 4), resilon-epiphany+composite (Group 5), and resilon-epiphany+MTA (Group 6). Fracture resistance of all samples was measured using the Instron testing machine. Three samples from each group had the depth of their fracture line measured by Micro CT Scan...

Ge nanocrystals formed in silica by implantation with 1.0 MeV Ge ions and subsequent annealing at 1100°C were characterised by transmission electron microscopy and Raman spectroscopy. The nanocrystals were found to be approximately spherical in shape and

The concept of compressive sensing was recently proposed to significantly
reduce the electron dose in scanning transmission electron microscopy (STEM)
while still maintaining the main features in the image. Here, an experimental
setup based on an electromagnetic shutter placed in the condenser plane of a
STEM is proposed. The shutter blanks the beam following a random pattern while
the scanning coils are moving the beam in the usual scan pattern. Experimental
images at both medium scale and high resolution are acquired and then
reconstructed based on a discrete cosine algorithm. The obtained results
confirm the predicted usefulness of compressive sensing in experimental STEM
even though some remaining artifacts need to be resolved.; Comment: 7 pages, 5 figures

Aim: To measure the fracture resistance of over-flared roots filled with a variety of materials (gutta-percha-nano HA, resilon-epiphany, composite and mineral trioxide aggregate - MTA) using the Instron machine test and micro-computed tomography (Micro CT) Scan. In addition, scanning electron microscopy (SEM) images were used to illustrate the type of fracture patterns of the specimens. Methods: One hundred and twenty extracted human mandibular singlerooted premolars were selected. A total of 105 out of the selected teeth were prepared to the working length and over-flared, leaving the apical 5 mm undisturbed. Fifteen samples had no treatment and were used as a positive control group (Group +ve). The 105 test teeth were further divided into 7 groups of 15 samples each. One of the 7 groups was designated as negative control (Group -ve) where teeth were over prepared and left without obturation. Remaining groups were filled with gutta-percha-nanoHA (Group1), gutta-percha-nano HA+composite (Group 2), gutta-percha-nano HA+MTA (Group 3), resilon-epiphany (Group 4), resilon-epiphany+composite (Group 5), and resilon-epiphany+MTA (Group 6). Fracture resistance of all samples was measured using the Instron testing machine. Three samples from each group had the depth of their fracture line measured by Micro CT Scan...